1. Technical Field
The present invention relates to a composite video multiplexing scheme and, more particularly, to a scheme for allowing multiple low bit rate video signals to be multiplexed into a single coded signal.
2. Prior Art
There are many instances where a number of separate video signals are to be transmitted to a single location. For example, security systems often use a number of cameras that all transmit their signals to a single monitor. A conventional monitor may function by xe2x80x9cscanningxe2x80x9d through each video, spending only a few seconds viewing each scene in sequence. As a result, there is a significant time lapse between sequential viewings of any particular scene. That is, if there are six sources and each is viewed for five seconds, there will be at least a 30 second time lapse (in the ideal case) between sequential viewings of any particular scene. Such a delay is unacceptable in many situations, particularly in security monitoring. Another technique utilizes a xe2x80x9csplit screenxe2x80x9d, such as xe2x80x9cquadrantxe2x80x9d viewing, where a number of separate scenes are simultaneously viewed. Although quadrant viewing solves the time lapse problem mentioned above, significant detail may be lost, since only one-fourth of the screen is dedicated to each scene. Additionally, such xe2x80x9csplitxe2x80x9d screen viewing is limited in that, for most practical situations, no more than four screens can be realistically viewed at a time.
The need remaining in the prior art is addressed by the present invention, which relates to a composite video multiplexing scheme and, more particularly, to a scheme for allowing for multiple low bit rate video signals to be multiplexed into a single coded composite video signal.
In accordance with the teachings of the present invention, a coder module is associated with each source (camera) and provides a digital output signal, where each line of digital data includes both a source identifier and a xe2x80x9clinexe2x80x9d identifier for the video scene. This data is stored in a xe2x80x9cfirst-in-first-outxe2x80x9d (FIFO) buffer at the source. A multiplexer is coupled to the plurality of FIFO buffers and functions to sequentially read from each FIFO buffer and form a multiplexed digital signal. The digital signal is then transformed into an analog output signal, where the output signal thus a comprises a composite of the separate video sources. A decoder at the termination of the system performs a analog-to-digital conversion and then reads the xe2x80x9csourcexe2x80x9d and xe2x80x9clinexe2x80x9d information and functions to xe2x80x9csortxe2x80x9d the received information. The sorted signals are then reconstructed into the separate video images.
The composite transmission system of the present invention is suitable for use with any low information rate signals (electronic billboards, communication notices, weather information, etc.).
Various other features of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.